Schmidt hammer test method for field determination of physical properties of zeolitized tuff

Abstract

The L-type Schmidt hammer is a hand-carried impact instrument that was originally designed and developed to test the compressive strength of concrete. When properly impacted against a stiff material the device measures the amount of rebound of a spring-loaded hammer, with the rebound of the hammer being directly proportional to the strength of the material tested. Application of this instrument to rock, specifically water-saturated zeolitized tuff, is demonstrated through a set of correlation diagrams that relate Schmidt hammer rebound values, obtained from core samples and from the sites where samples were taken, to physical properties measured on rock samples in the laboratory. The properties include compressive strength, compressional and shear velocities, and dynamic and static Young's shear and bulk moduli. The correlation diagrams apply only to zeolitized tuff of the type found at the Nevada Test Site in its natural state (freshly excavated). These diagrams enable the user of the L-type Schmidt hammer to immediately obtain values of physical properties of such rocks in place, a convenience desirable where conventional sampling is not feasible or is impossible, and when results are required on short notice. The charts apply to L-type hammers that are calibrated to a nominal rebound value of 74. Calibration is made on a 35-pound-(16-kg-) test anvil with a steel-hardened test surface of Brinell hardness = 500 kg/mm 2 .